1. Field of Invention
The present invention relates to a sensing device, especially a micro-electro-mechanical sensing device and a manufacturing method thereof.
2. Description of Related Art
MEMS (Micro-Electro-Mechanical System) technology has opened up a whole new technology and industry; such technology is widely used in various fields. MEMS inertial sensors are a typical example of such technology, which for example include accelerometers and gyroscopes. In these sensors, a MEMS spring structure is usually required to fix one end of a moving structure on a side wall, so that this moving structure is capable of reciprocating motion in a specific direction. The related spring structure is usually composed by a stack of silicon layers or metal layers and oxide layers in alternative order.
However, due to different thermal expansion coefficients between the metal layer and the oxide layer, the high temperature process will result in thermal expansions of different degrees on the metal layer and the oxide layer, which cause the MEMS spring structure to distort and affect their performance. Therefore, how to prevent the MEMS spring structure from deformation affected by environment temperature changes and ensure good performance of the MEMS spring structure are important topics to this field.
Besides, in prior art, the MEMS spring is usually designed in the form of a horizontal layout, so the area left for other components on a substrate is reduced. In other words, how to effectively improve the area utilization efficiency or reduce the device size are important topics to this field.